The present disclosure provides techniques for externally generating and delivering electrical stimulation to a user/patient, particularly useful for external defibrillation of cardiac tissue. In external defibrillation applications, high voltage electrical pulses are generated to apply high joule (150 to 360 joules) shocks to the heart of a treated user/patient through electrodes connected to the chest area of the user/patient for treating cardiac dysrhythmias and ventricular fibrillation (e.g., sudden cardiac arrest). The electrical pulse generated by external defibrillators (also referred to herein as defibrillation pulse) is typically a decaying capacitive discharge pulse having a peak voltage between 1000 to 2000 volts, and a time duration of about 10 milliseconds.
The conventional external defibrillators, typically consisted of bulky hospital equipment confined for use in healthcare centers. Technological developments in capacitors and batteries production enabled development of portable defibrillators for use out of healthcare centers (e.g., in ambulances). The introduction of the biphasic defibrillation pulses allowed to significantly decrease defibrillation energy levels, which further led to development of automated external defibrillators that can be used without requiring any clinical skills.
Defibrillation devices and techniques known from the patent literature are briefly described herein below.
U.S. Pat. No. 5,395,395 describes a method for increasing the energy output from a number of charged capacitors each of the capacitors is discharged, one after another, through a load. The capacitors are then coupled in series in successive, different combination, each of which includes a part or all of the capacitors. These combinations are and being discharged, one after another, through the load. Also described an apparatus for increasing the energy output from a number of charged capacitors utilizing a charging circuit, arranged to control the charging of the capacitors, and a controllable switching device, arranged to first connect each of the capacitors to a load for discharge of the capacitors, on after another. The switching device then couples the capacitors in series in successive, different combinations, each of which includes a part or all of the capacitors, and connects the respective combinations to the load for discharge of the series couplings, on after another.
U.S. Pat. No. 5,507,781 suggests to use switches to set the topology and polarity of a circuit that includes capacitors to deliver an electric pulse to a heart during a defibrillation procedure. The waveform of the electric pulse is bi-phasic, in that it is a positive portion of the pulse followed by a negative portion of the pulse. The topology and polarity of the circuit are utilized to produce a waveform that approximates the ideal waveform for the specific situation. The circuit provides for combinations of capacitors variously in series and in parallel and changing the topology and polarity of the circuit during discharge of the capacitors.
U.S. Pat. No. 6,241,751 a defibrillator having an energy storage capacitor network with multiple configurations selected according to patient impedance and desired energy level for delivery of an impedance-compensated defibrillation pulse. The set of configurations may include series, parallel, and series/parallel combinations of energy storage capacitors within the energy storage capacitor network. The impedance-compensated defibrillation pulse may be delivered over an expanded range of energy levels while limiting the peak current to levels that are safe for the patient using configurations tailored for lower impedance patients and limiting the range of defibrillation pulse durations and providing adequate current levels for higher impedance patients. Configurations of the energy storage capacitor network may be readily added to extend the range of energy levels well above 200 joules.
General Description
Automated external defibrillation (AED) devices configured for home use are life saving devices designed to be applied on a chest area of a user by electrode pads, sense heart rhythm of the user, and deliver electric shocks to the user's body if certain cardiac arrest conditions are identified. These devices are typically arranged in form of a suitcase designed for household storage, but they are not designed to be comfortably carried by a user during outdoor activities.
Embodiments of the present application provide a handheld lightweight (e.g. of about 350 grams) AED device of substantially reduced size/dimension, that can be easily placed in a front pocket of a shirt or a pouch, or attached to the user's body by belt and/or straps i.e., freeing the user's hands. Thus, the AED device disclosed herein can be easily carried on (e.g., in/on a clothing article or on the user's body) during day and night time activities, or sleep, and instantly activated by the user, and/or a helper e.g., family member, work colleague, passer-by, to deliver defibrillation shocks to the heart of the user in cardiac specific arrhythmias events.
The size and weight of the defibrillators disclosed herein are considerably reduced in some embodiments by, at least, special designs and arrangements of an energy storage unit (ESU) of the defibrillator, and/or of a pulse delivery unit thereof. In some embodiments, the defibrillator is configured to enter first into a standby mode upon activation of the device, in which the ESU is partially charged to a predefine percentage of the required defibrillation voltage, and thereafter it is fully charged to the defibrillation voltage whenever it is determined that a defibrillation pulse is to be applied to the user's body.
Optionally, and in some embodiments preferably, in comparison with the previous art using bulky relays physically disconnect the pads from the rest of the defibrillator to prevent an accidental electrocution, this invention discloses a miniature motorized electro-mechanical contactor to physically isolates the defibrillation pads from the electronic circuits of the defibrillator at any time except when needed, to prevent an accidental electrocution.
In the following disclosure, the ESU comprises a plurality of serially connected small sized capacitive elements (also referred to herein as a capacitor bank), each having a relatively large capacitance value (e.g., about few hundreds of μF) and its own respective charging unit configured to controllably charge each capacitive element of the capacitor bank to a predefined portion of the total voltage needed for defibrillation. In this way, the serially connected capacitive elements can be safely charged to their maximal required voltage levels (e.g., about 2,000 Volts) without using the voltage equalizing resistors ladder, typically required in such serial connection of capacitive cells, thereby compacting the geometrical dimensions and minimizing power loses of the capacitor bank that, typically, occur in conventional designs due to the discharge currents through the voltage equalizing resistors ladder.
Optionally, and in some embodiments, preferably, the capacitive elements used in the ESU (also referred to herein as “storage capacitors”) are meticulously examined for selecting capacitive elements having a leakage current within a 5% limit, which, thus, allow constructing the capacitors bank without the conventional equalizing resistors ladder typically required in such implementations. Thus, in some embodiments, when repairing is needed due to a defective capacitive element of the ESU, the entire capacitors bank is replaced to assure that all capacitive elements of the capacitors bank have the same leakage current characteristics. Thus, in some embodiments, the capacitors bank is a removable unit. Optionally, and in some embodiments, preferably, the capacitive elements in the capacitors bank are inseparably attached to each other (e.g., glued together) to prevent separately replacing a defective capacitive element thereof, and assure that the entire capacitors bank is replaced.
In the ESU, the use of a plurality of capacitive elements having, each, a relatively large capacitance value and small geometrical dimensions (relative to capacitive elements used in the previous art), permits substantial compact designs of the charging units of the defibrillators disclosed herein. Further compactness is achieved by utilizing significantly small sized voltage converters (DC/DC converters) to charge each of the storage capacitors.
As described herein below in details, and illustrated in the drawings, this ESU configuration enables substantially compact arrangements of the plurality of relatively small sized storage capacitors and their respective compact charging units into a compact unit. The pulse delivery unit (also referred to herein as an insulated gate IGBT transistor unit) comprises, in some embodiments, a specially designed low power H-bridge circuit configured to convey the electric charges stored in the storage capacitors bank to the electrode pads of the device as a bi-polar defibrillation pulse. Switching circuitries of the H-bridge are activated in some embodiments, by respective isolated drivers powered by respective driver capacitors. In this way, a single and small voltage converter (DC/DC converter) device is used in the pulse delivery unit to electrically charge the driver capacitors to a level sufficient to drive the IGBT transistors of the H-bridge circuit. With this design, the pulse delivery unit can be also arranged to provide small-sized compact structures.
The small-sized compact arrangements of the ESU, of the pulse delivery unit, and of other components of the defibrillator, as described herein below in details, permits small-sized compact arrangements enabling minimizing the geometrical dimensions of the defibrillator into a handheld device e.g., like a thicker smartphone in shape and size.
In a broad aspect, there is provided a handheld defibrillation device connectable to defibrillation pads and comprising a single low voltage and small size battery cell for supplying electrical power the entire defibrillator device, an energy storage unit comprising a plurality of capacitive elements, and a charger setup configured to independently and separately charge each of the plurality of the capacitive elements for outputting by the energy storage unit a determined high voltage level. Optionally, and in some embodiment preferably, the voltage of the single battery cell is smaller than 5 volts. In some embodiments, the determined high voltage level outputted by the energy storage unit is greater than 1,000 volts.
The charger setup can comprise a plurality of charging circuitries, each of the charger circuitries being electrically connected to the single battery cell and configured to charge a respective one of the plurality of capacitive elements of the energy storage unit. A pulse delivery unit is used, in some embodiments, to discharge the capacitive elements through the defibrillation pads in a desired pulse form into a body of a subject.
Optionally, and in some embodiments preferably, each capacitive element of the energy storage unit is serially electrically connected to at least one other capacitive element of the energy storage unit, and wherein, each charging circuitry of the charger setup is being configured to independently and separately deliver electrical charges from the single battery cell to its respective capacitive element in the energy storage unit, to thereby, build the determined high voltage level over the plurality of serially connected capacitive elements.
One inventive aspect of the subject matter disclosed herein relates to a handheld defibrillation device connectable to defibrillation pads for the application of one or more defibrillation pulses. The defibrillation device comprises in some embodiments a single low voltage small size battery cell, an energy storage unit comprising a plurality of capacitive elements, a charger setup comprising a plurality of electric charger circuitries/charging cells, each of said charger circuitries being electrically connected to the battery cell and configured to charge a respective one of the plurality of capacitive elements, and a pulse delivery unit configured to discharge the capacitive elements through the defibrillation pads in a desired pulse form into a body of a subject.
The capacitive elements can be arranged to implement a capacitors bank using a respective plurality of serially connected storage capacitors as its capacitive elements. The pulse delivery unit can be configured and arranged to discharge electrical charges of the serially connected storage capacitors through the defibrillation pads to a body of a subject.
In some embodiments, the defibrillation device is a handheld flat device having a smartphone-like shape and a thickness smaller than 25 mm.
In some embodiments, each electric charging cell comprises a respective one of the storage capacitors serially connected to at least one other storage capacitor of another cell. Each charging circuitry can be configured to, independently and separately, deliver electrical charges from the battery cell to its respective storage capacitor for obtaining a determined voltage level over the capacitors bank. The charging circuitry of each charging cell is configured, in some embodiments, to independently prevent the voltage level over its respective storage capacitor from exceeding a maximal allowable voltage level on the storage capacitor. Optionally and in some embodiments, preferably, operational features of the storage capacitors are selected to permit the energy storage unit to charge the storage capacitors without a voltage equalizing resistors ladder.
Optionally, and in some embodiments, preferably, the number of serially connected storage capacitors in the energy storage unit varies according to properties of the subject, such as, but not limited to, age and/or weight. Thus, the defibrillation device can be a modular device, which may be manufactured in various, different dimensions and energy storage capacitors.
In some possible embodiments, the pulse delivery unit comprises two upper and two lower IGBT blocks (also referred to herein as switching blocks) arranged in a H-bridge structure configured to discharge the charge stored in the plurality of serially connected storage capacitors through the defibrillation pads in a form of a bi-polar defibrillation pulse. Each IGBT block of the pulse delivery unit can comprise a switching circuitry and a respective capacitive element (also referred to herein as a “driver capacitor”) configured to store electrical charge for generating a driving current sufficient for changing the IGBT block into an electrically conducting state for delivering the defibrillation pulse. In this way, the IGBT blocks can be arranged to form a H-bridge circuit configured to couple the defibrillation pads to the energy storage unit (ESU). Each IGBT block comprises a controllable driver unit for the IGBT transistor and a driver capacitor configured to power the controllable driver unit to controllably generate the driving current for changing the state of the respective IGBT block into the electrically conducting state when needed.
Advantageously, the H-bridge comprises a single and small power regulator using a voltage converter to supply electric power from the battery cell to the IGBT blocks of the H-Bridge for charging their driver capacitors. Optionally, and in some, embodiments preferably, the voltage converter comprises a small sized flyback converter (403 in FIG. 4A). In some possible embodiments, the ground terminal of the driver capacitor of each IGBT block is electrically connected to a respective rail of said IGBT block, the high voltage terminals of the switching circuitries of the upper IGBT blocks are electrically connected to the energy storage unit for discharging its capacitive elements, a rail of each one of the upper IGBT blocks is electrically connectable to a respective one of the defibrillation pads, a high voltage terminal of the switching circuitry of each one of the lower IGBT blocks is electrically connected to the rail of a respective upper IGBT block, and the lower rails of the lower IGBT block are electrically connected to an electrical ground of the device
The pulse delivery unit is configured in some embodiments, to charge the driver capacitors of the lower IGBT blocks of the H-bridge structure upon activation of the single power regulator/voltage converter. The pulse delivery unit can be configured to charge the driver capacitors of the upper IGBT blocks of the H-bridge structure only after charging the driver capacitors of the lower IGBT blocks, by changing the switching circuitries of the lower IGBT blocks into an electrically conducting state.
In some embodiments, the defibrillation device comprises a control unit configured and operable to activate the charging circuitries of the charger setup of the energy storage unit, activate the power regulator/voltage converter for powering the pulse delivery unit, and to generate control signals for the controllable driver units of the lower switching blocks to charge the driver capacitors of the upper switching blocks after the charging of the driver capacitors of the lower switching blocks. Optionally, and in some embodiments, preferably, the control unit is configured and operable to generate control signals for the controllable drivers to activate a predetermined switching sequence of the switching circuitries of the IGBT blocks and thereby, to discharge the storage capacitors of the energy storage unit in a form of a bi-polar defibrillation pulse. The control unit can be configured to activate the charging circuitries of the charger setup of the energy storage unit and to activate the predetermined switching sequence of the IGBT blocks in response to either a user input or an alarm indication received from an external device.
In a possible embodiment, an impedance measurement unit is used for measuring impedance between the defibrillation pads and for generating measurement data indicative thereof. The control unit is configured and operable to process the measurement data obtained from the impedance measurement unit and to activate the predetermined switching sequence of the IGBT blocks if the measured impedance is within a predetermined range.
The device can also comprise a wireless communication module configured and operable to exchange data with and through a data network. The control unit can be configured and operable to communicate data with a computerized device (e.g., a smart device, such a smartphone of the user) during operation of the defibrillation device.
The device comprises, in some embodiments, a case, a display unit provided in the case, and a movable capsule (also referred to herein as cover) having closed and open states relative to the case. The capsule can be configured and arranged to accommodate the defibrillation pads and their connecting cables and to cover a portion of a display area of the display device in the closed state, to thereby provide at least part of the display visible for displaying information in the closed state. Optionally, and in some embodiments, preferably, the capsule is configured and arranged to hermetically seal the defibrillation pads and the connecting cables contained therein while in the closed state.
The capsule comprises, in some embodiments, at least one charging induction coil configured and arranged to wirelessly charge an external device (e.g., a heart monitor configured to provide wirelessly the ECG related signals of the subject to the defibrillation device). One or more support elements can be provided on the capsule for positioning the external device in proximity to the charging induction coil to maximize the wireless transfer of charging energy thereto. Optionally, the capsule and/or the case of the defibrillator unit may comprise wireless circuitry for wirelessly charging the defibrillator internal single cell battery. Both the capsule and the case may comprise guiding mechanical elements to precisely position the external wireless charger with the respective charging device to maximize the magnetic flux for charging.
Advantageously, the storage capacitors of the ESU may have a leakage current in the range of tens of microamperes, to thereby provide a relatively sure and short self-discharge time for reducing electrical shock hazards.
Another inventive aspect of the subject matter disclosed herein relates to a method of applying a defibrillation pulse to a subject via electrode pads. The method comprising separately and independently charging a plurality of serially connected storage capacitors by a plurality of respective charging units, measuring the overall voltage over the plurality of serially connected storage capacitors and generating measurement data indicative thereof, and processing the measurement data and discharging electrical charges accumulated in the serially connected storage capacitors via the electrode pads upon determining that the voltage over the serially connected storage capacitors reached a predetermined defibrillation voltage level.
In some possible embodiments, the method comprises charging the plurality of serially connected storage capacitors until a predefined standby voltage level is obtained over the serially connected storage capacitors, receiving an indication that the defibrillation pulse is to be applied (e.g., a user input and/or an alarm/alert from an external device), charging the plurality of serially connected storage capacitors until the predetermined defibrillation voltage level is obtained over the serially connected storage capacitors, and discharging electrical charges accumulated in the serially connected storage capacitors via the electrode pads.
To permit the charging of the storage capacitors without a voltage equalizing resistors ladder, the charging process comprises, in some embodiments, comparing the voltage over each storage capacitor with an allowable reference voltage, and halting operation of the respective charging unit used for the charging of the storage capacitor whenever the voltage thereover reaches, or exceeds, the allowable reference voltage. The method may further comprise selecting and matching features of the capacitive elements, such as capacity and leakage current, so as to prevent possible damages that may be caused due to overcharging them. Once matching each other, the capacitive elements can be safely charged to voltage levels of about their maximal allowable voltages without a voltage equalizing resistors ladder.
Optionally, and in some embodiments, preferably, the discharging of the electrical charge accumulated in the storage capacitors comprises using a H-bridge structure of two upper and two lower IGBT blocks powered by a single power source/voltage converter to deliver a bi-polar defibrillation pulse. Each of the IGBT blocks comprises an IGBT transistor circuitry and a respective driver capacitor electrically connected to the power source and configured to accumulate electrical charges for changing the state of the respective IGBT transistor to a conductive state. The method can, thus, comprise activating the voltage converter of the single power source for charging the driver capacitors of the lower IGBT blocks and thereafter turning the switching circuitries of the lower IGBT blocks into a conductive state for charging of the driver capacitors of the upper IGBT blocks by providing an indirect path to the ground through the IGBT's transistors of the lower switching blocks.
The method comprises, in some embodiments, measuring the electric impedance between the electrode pads and applying the defibrillation pulse if the measured impedance is within a predefined impedance range. Additionally, or alternatively, the method comprises measuring ECG signals of the subject and applying the defibrillation pulse if the measured ECG signals are indicative of irregular, or specific abnormality of heart activity.
Yet, another inventive aspect of the subject matter disclosed herein relates to a pulse delivery device for discharging the electrical charge from a capacitors bank through two electrodes. The pulse delivery device comprises two upper and two lower IGBT blocks arranged to form a H-bridge structure and a single power source. Each of the IGBT blocks comprises a controllable IGBT based circuitry, a respective driver capacitor configured to store electrical charges from the power source for changing the IGBT based circuitry into an electrically conducting state, a rail for connecting between ground terminals of the controllable switching circuitry and of the respective driver capacitor. The rails of the lower IGBT blocks being connectable to an electrical ground, and the rail of each upper IGBT block being configured to establish electrical connection with said electrical ground via a controllable switching circuitry of respective one of the lower IGBT blocks.
The pulse delivery circuitry is configured, in some embodiments, to charge the driver capacitors of the lower IGBT blocks of the H-bridge structure upon activation of the single voltage converter. The circuit can be configured to charge the driver capacitors of the upper IGBT blocks of the H-bridge structure after charging the driver capacitors of the lower IGBT blocks, by changing the IGBT transistors of the lower IGBT blocks into an electrically conducting state.
Optionally, and in some embodiments, preferably, the device comprises a controllable driver unit in each of the IGBT blocks. The driver capacitor of each one of the IGBT blocks is configured to power its respective controllable driver unit to controllably generate a driving current for changing the state of the respective IGBT transistor of the IGBT block into the electrically conducting state.
In some embodiments, the common ground terminal of both the driver capacitor of the controllable driver and of the IGBT transistor, of each IGBT block, is electrically connected to the respective rail of the IGBT block, high voltage terminals of the switching circuitries of the upper IGBT blocks are electrically connected to the capacitors bank, the rail of each one of the upper IGBT blocks is electrically connectable to a respective one of the electrode pads, a high voltage terminal of the switching circuitry of each one of the lower IGBT blocks is electrically connected to the rail of a respective upper IGBT block, and the rails of the lower IGBT block are electrically connected to the electrical ground of the device.
In some embodiments, each IGBT block comprises a small sized flyback converter configured to use the same single small size and low voltage battery cell of the device for the simultaneous charging of the respective storage capacitors. The term single cell battery as used herein, means a battery whose voltage is dictated by the manufacturing chemistry, and not by interconnecting it serially with other cells to increase the overall voltage of the battery. By example, typically, a single cell battery based on Li chemistry has a voltage of 3.7V.
It is thus appreciated that the defibrillator devices disclosed herein are powered entirely by a single cell battery.